Background -- Hybridization and polyploidization are considered important driving forces of invasive processes. In the invasive Fallopia spp. complex, hybridization between taxa of various ploidy levels ... [more ▼]

Background -- Hybridization and polyploidization are considered important driving forces of invasive processes. In the invasive Fallopia spp. complex, hybridization between taxa of various ploidy levels has been experimentally demonstrated. Extensive genetic variation has also been observed among hybrids in the field. However, what makes a certain hybridization event of evolutionary importance is still the subject of speculation considering the invasive potential of hybrid Fallopia. Aims -- The present study examined landscape scale patterns of interspecific hybridization within the alien invasive Fallopia complex, and tested whether cold winter might act as selective agent for hybrid survival. Methods -- Eighty seeds per clone were collected from four taxa (F. japonica, F. sachalinensis, F. aubertii, and F. xbohemica) and sown in greenhouse and outdoor conditions. Ploidy levels of the resulting seedlings were determined by flow cytometry at early stages of seedling growth and compared to those of mature clones present in the same landscapes. Key results -- The four studied taxa were involved in interspecific hybridization patterns. Seedlings resulting from hybridization had a large range of ploidy levels, including aneuploid and euploid progeny, and polyploid levels that were not observed in mature clones. Cold winter had a negative effect on germination success. However, a comparison of ploidy levels of seedlings that survived the cold winter with those grown under greenhouse conditions indicated that cold winter was not a significant selection agent for particular ploidy levels. Conclusions -- Our results stress the importance of interspecific hybridization and polyploidization events in generating invasive hybrids in the alien Fallopia spp complex. Cold winter represents a selection agent for the survival of early stages of progeny but does not explain the discrepancies in ploidy levels between produced seedlings and currently occurring mature clones. [less ▲]

In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the ... [more ▼]

In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the processes underlying invaders’ success. However, the extent to which scientists have worked on the integration of the ecology and evolution of invasive plants is poorly documented, as few attempts have been made to evaluate these efforts in invasion biology research. Such analysis can facilitate recognize well-documented relationships and identify gaps in our knowledge. In this study, we used a network-based method for visualizing the connections between major aspects of ecology and evolution in the primary research literature. Using the family Poaceae as an example, we show that ecological concepts were more studied and better interconnected than were evolutionary concepts. Several possible connections were not documented at all, representing knowledge gaps between ecology and evolution of invaders. Among knowledge gaps, the concepts of plasticity, gene flow, epigenetics and human influence were particularly under-connected. We discuss five possible research avenues to better understand the relationships between ecology and evolution in the success of Poaceae, and of alien plants in general. [less ▲]

Japanese knotweed Fallopia japonica is an extremely abundant invasive plant in Belgium and surrounding countries. To date, no eradication method is available for managers facing the invasion of this ... [more ▼]

Japanese knotweed Fallopia japonica is an extremely abundant invasive plant in Belgium and surrounding countries. To date, no eradication method is available for managers facing the invasion of this rhizomatous plant. We tested different chemical herbicides and two application methods (spraying and stem injection), as well as mechanical treatments, on Fallopia clones throughout southern Belgium. The tested methods were selected to be potentially usable by Belgian managers, e.g. using legally accepted rates for herbicides. Stem volume, height and density reduction was assessed after one or two years depending on the treatment. No tested method allowed a complete eradication of the clone. However, stem injection with glyphosate-based herbicide caused the highest damage. The year following injection, no sprouts were observed. Two following year, however, stunted shoots sprouted. Among mechanical control measures, repeated cuts combined with native trees cuttings plantations most appreciably reduced knotweed development. The most efficient methods we tested appear as tools for curbing knotweed invasion but are not likely to be used to eradicate the species. As such they should be included in a more integrated control strategy, together with prevention and public awareness campaigns. [less ▲]

Cotoneaster horizontalis DECAISNE, a Rosaceae coming from Asia, was introduced in Belgium as an ornamental species. Different sides of the invasion were studied, from the distribution of the species and ... [more ▼]

Cotoneaster horizontalis DECAISNE, a Rosaceae coming from Asia, was introduced in Belgium as an ornamental species. Different sides of the invasion were studied, from the distribution of the species and the invasion status, the impacts, to management methods. To describe the invasion status, information was gathered about the occurrence and the distribution of the species in Belgium by compiling various databases. The naturalization status in calcareous grasslands, high-value habitats recognized as biodiversity hotspots, was assessed. Occurrence, population status, preferred habitats, invaded communities, growth rate and fruiting capacity were characterized. Once naturalization established, we investigated its impacts on calcareous grasslands communities, individual species and pollinators. C. horizontalis occurred in seven of the nine studied calcareous grasslands, with densities from 0.34 to 10 individuals/ha. In the most invaded sites, an ongoing colonization process was suggested by a high proportion of small individuals. Moreover, 3-year-old individuals already showed fruiting capacities. Germination rate reached about 30%. Significant impacts on habitat structure and vegetation were showed. Community structure and composition changes were demonstrated in invaded sites by decreasing species richness and diversity. As calcareous grasslands are priority Natura2000 habitats, measures must be taken to control the spread of C. horizontalis. For this purpose, we performed management tests to identify the most efficient techniques that would help the restoration of calcareous grasslands. Both mechanical and chemical management techniques were tested. Methods choice was driven by the environmental constraints of calcareous grasslands, which require highly selective techniques, and by species characteristics. Tested methods were cuttings, stump burning, spraying, cutting plus glyphosate application on stump and glyphosate application on stem basis. Efficiency, cost, feasibility and side-effects on ecosystems were estimated. Management tests are still ongoing but some results have already been drawn: spraying and single cutting are not efficient, the last one generating production of numerous sprouts. Finding the best management method will not be sufficient to stop the invasion. C. horizontalis is still present in 53% of the sale catalogs of horticulturists in Southern Belgium. As long as the species is used in the vicinity of calcareous grasslands, propagules are continuously provided, jeoparding management actions. [less ▲]

In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the ... [more ▼]

In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the processes underlying invaders' success. However, the extent to which scientists have worked on the integration of the ecology and evolution of invasive plants is poorly documented, as few attempts have been made to evaluate these efforts in invasion biology research. Such analysis can facilitate recognize well-documented relationships and identify gaps in our knowledge. In this study, we used a network-based method for visualizing the connections between major aspects of ecology and evolution in the primary research literature. Using the family Poaceae as an example, we show that ecological concepts were more studied and better interconnected than were evolutionary concepts. Several possible connections were not documented at all, representing knowledge gaps between ecology and evolution of invaders. Among knowledge gaps, the concepts of plasticity, gene flow, epigenetics and human influence were particularly under-connected. We discuss five possible research avenues to better understand the relationships between ecology and evolution in the success of Poaceae, and of alien plants in general. [less ▲]